The major objectives of this work are as follows: To standardize the technique for pacing the diaphragm in patients with chronic ventilatory insufficiency. To determine the optimal electrical parameters for pacing the diaphragm with particular emphasis on muscle conditioning. To define definitively the conditions for which diaphragm pacing is indicated and especially to identify those patients in whom a less than optimal response can be expected and to determine a plan for management. To explore in the laboratory, and eventually in the clinic, a newly developed totally implantable multiprogrammable hybrid circuit neural stimulator.